Formation of in-plane crystals of molecular organic semiconductors

Molecular organic semiconductors have recently been applied widely as active layers in electronic and optoelectronic devices such as organic field-effect transistors and light-emitting devices. The use of organic active layers derives both from materials considerations and from processing advantages. The goal is to enable novel applications and structures that are difficult to produce with conventional materials (e.g., large-area, flexible, or transparent devices). Because charge transport efficiency increases with improved molecular ordering, the formation of large-area single crystals of these materials is essential for achieving integrated active organic structures. This thesis presents (1) an investigation of substrate surface modification as a means of inducing order within polycrystalline organic thin films, and (2) a new method for oriented, in-plane growth of millimeter-scale single crystal needles of molecular organic semiconductors. Two types of modified surfaces are investigated: (a) self-assembled nanofilms (SANFs), and (b) submicron periodic surface-relief structures. Polycrystalline thin films of pentacene and tetracene are vacuum sublimed onto pre-modified substrates. This work initially evaluates the influence of organosilane SANFs on morphology and field-effect transistor performance. It then attempts to use lithographically-defined surface relief to orient pentacene and tetracene grains via graphoepitaxy during thin film deposition. The periodic surface relief selects several preferred grain orientations, but uniaxial in-plane orientation is prevented by insufficient interfacial tension anisotropy.

Department dc:contributor.department

Massachusetts Institute of Technology. Dept. of Materials Science and Engineering.

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

2004

Author dc:creator

• Mascaro, Debra Jane Lightly, 1972-

Advisor dc:contributor.advisor

• Vladimir Bulović, Timothy M. Swager and Michael F. Rubner .

• Materials Science and Engineering.

Statement dc:rights

• M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission.

Licence dc:rights.uri

• http://dspace.mit.edu/handle/1721.1/7582

Language dc:language.iso

eng

Handle dc:identifier.uri

http://hdl.handle.net/1721.1/32266

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/32266